Colorant compositions are useful for a wide variety of product applications. For example, colorants are used in tinting of polymers, for providing coloration to aqueous solution(s), and affording color to solid or semi-solid products such as detergents. Crayons, ink compositions, toilet bowl colorants, plastics, soaps, and many other products are colored using triphenylamine-based colorant compositions.
Triphenylmethane (“TPM”) colorants consist of three aromatic rings linked by a central carbon atom. TPM colorants can be prepared by first condensing an aromatic aldehyde with two equivalents of an aromatic amine (which will hereafter be referred to as the “coupler” or “coupling component”) in the presence of an acid such as sulfuric acid, phosphoric acid, or muriatic acid. After condensation, the uncolored intermediate is oxidized using a variety of oxidizing agents (hydrogen peroxide, lead oxide, chromium oxide) to afford the TPM colorant. Variations in the substitution patterns on either the aldehyde or the coupler molecules can change slightly the wavelength of light absorbed, thus providing a different color to the colorant species. The substitution of groups in this manner is highly unpredictable. A large amount of effort may be expended to find the right molecular combination to provide the most appropriate color shade for a given application.
One problem with TPM colorants is inadvertent or undesirable discoloration. This may occur if an undesirable chemical reaction occurs to the colorant molecular species. In the case of TPM based colorants, nucleophilic groups such as OH— or certain basic amine. groups may react with and undesirably decolorize or shift the shade of such colorants. It is known that at elevated pH levels, TPM based colorants are subject to hydroxyl (OH—) attack. These reactions may undesirably decolorize or change the shade of the colorant molecule. Thus, it would be highly desirable to develop compositions, methods, or techniques that could be used for affording color in such product applications while providing a high level of stability in alkaline environments as well. This ensures that adequate color remains, even under alkaline conditions.
Discoloration of TPM colorants and or dyes has been addressed in a number of patents, some of which are discussed below.
The Ragsdale patent (U.S. Pat. No. 6,395,797), discloses organic cyclic ester additives formulated with TPM colorants to reduce color degradation in polyurethane foam systems caused by certain tertiary amine catalyst.
In Harris (U.S. Pat. No. 6,342,618), TPM colorants containing sterically hindered fugitive amine counterions employed to improve stability of such colorants in inks. The Triphenylmethane polymeric colorants are capped with a cyclic anhydride. The sterically hindered amine counter ions are those based on low molecular weight fugitive tertiary amines, such as N,N-dimethylethanolamine.
U.S. Pat. No. 3,927,044 (Foster et al.) discloses alkaline stable fugitive tints prepared using aromatic aldehydes containing an electron-withdrawing group (X) in the ortho-position. These fugitive tints are prepared with highly ethoxylated aromatic amines. The tints are said to exhibit improved lightfastness and provide some degree of alkaline stability.
Stability is defined in this Foster patent disclosure as the ability to retain color in an alkaline solution at a pH level of 11. The X in the structure represents the electron-withdrawing group in the ortho position and may include halogen, nitro, or sulfonyl radicals.
U.S. Patent Publication No. 2004/0143910 A1 discloses the use of certain triphenylmethane dyes as hair colorants, which are resistant to decolorization in alkaline bleach medium. This patent teaches that TPM dyes containing deactivating (electron withdrawing) or weakly activating groups substituted at the ortho- and/or para-positions relative to the central methane carbon and/or auxochrome groups (located on or attached to the aromatic rings of the TPM) have enhanced survival in alkaline bleach medium. As more and more groups are added to the rings, stability increases proportionally, so that dyes with the most substituents on all three aromatic rings are the most stable. These deactivating and protective groups may be nitro, halogen, cyano, carboxyl, sulfonic, alkyl, or aromatic groups, but not amino, hydroxy, alkoxy or alkylamide groups. In this patent auxochromes are defined as weakly basic groups such as hydroxy or amino groups. If the auxochrome is an amino group, it may be a primary amino group (—NH2), a secondary amino group (—NHR1), or a tertiary amino group (—NR2) where R1 and R2 may be identical or different, and either may be alkyl, alkoxy, carboxy, cyano, alkyl cyano, halogen, phenyl, or naphthyl substituent.
U.S. Pat. No. 4,595,536 (Hung et al) discloses TPM dyes of the structure shown below.

These dyes are reported to be resistant or stable enough to sanitizing agents, which produce hypochlorite in aqueous solutions, that they can be used in automatic toilet bowl sanitizers. In this patent disclosure, X represents hydrogen or hydroxy. M represents an alkali metal cation, an ammonium ion, or an alkaline earth metal cation.
An additional patent by Hung et al, U.S. Pat. No. 4,632,783 discloses TPM dyes of the structure shown below.

These dyes are reported to be resistant or stable enough to serve as sanitizing agents, which produce hypochlorite in aqueous solutions. They can be used in automatic toilet bowl sanitizers. In this patent, X represents hydrogen or the group SO3M. Y represents hydrogen or hydroxy. M represents an alkali metal cation, an ammonium cation, or an alkaline earth metal cation.
U.S. Patent No. 2004/0214918 A1 (Banning et al.) is directed to colorant compositions having aromatic ring structures with an attached nitrogen, in which the nitrogen is substituted with an R group, and also with an alkylene oxide containing structure. The R group may be alkyl, aryl, arylalkyl or an alkylaryl group. Further, the R group may be joined to the phenyl moiety to form a bicylic structure. The overall triphenyl-based structure proposed in this patent contains one alkylene oxide chain (CnH2nO)xH attached to the nitrogen. This alkylene oxide chain is derived from its presence on the aromatic aldehyde that is reacted two other phenyls to form the triphenyl-based structure. The non-ring based carbon of the aromatic aldehyde group forms the central carbon of the triphenylamine-based structure that is formed.
Shikhaliev et al (Khimiya I Khimicheskaya Tekhnologiya, 1999, Vol. 42, No. 4, pp 83–87) reported the preparation and spectral properties of the following TPM dyes of the structure shown below where R1 is H or NMe2 and R is H or Me.

U.S. Pat. No. 5,591,833 to Hines et al is directed to fugitive tint materials that are more easily removed from yarns without scouring the yarns. The Hines patent discloses colorants and compositions useful as fugitive or permanent colorants for a variety of substrates, and having one or more improved properties, such as: enhanced aqueous washability, reduced staining, compatibility with and non-extractability from thermoplastic resins, and reactivity with resins having reactive functionality.
The compositions disclosed in Examples 63, 64, and 65 of the Hines patent incorporate long chain ethylene oxide (EO) residues containing at least two glycidols (denoted “GL” in the patent) attached to nitrogen. Example 63 contains two “H-50 EO/2GL-” groups, while Examples 64 and 65 disclose two “H-10 EO/2GL-” and two “H-50EO/2GL-” groups, respectively, attached to separate nitrogens annexed to a triphenylmethane-based compound. Hines discloses using between 2 and 6 glycidol residues attached to a nucleophilic site.